Quellenforschung

"Source investigation."
Historians try to puzzle out the sources of an ancient author's work by looking
closely at clues like the author's dates (if known), biases exhibited in all
or parts of his work, odd enthusiasms, or opinions which seem more appropriate
to an author of an earlier age. (For example, if an E2 writeup were to speak
of the dangers of Soviet communism today, you'd quickly guess that the noder
had looked at literature from the cold war era.) The game is played by ransacking
lists of authors who wrote (or probably wrote) at an earlier date and looking
for ones who seem to match the picture called for by the clues gathered from
the work of the author under investigation. Sometimes the evidence does not
point to someone known but to a putative "author X" who matches it.

Quellenforschung flourished
because ancient historians were indifferent about citing their sources, whereas
moderns are keen to know which 'facts' an ancient author reports can be trusted
and how much. Knowing an ancient historian's source would offer a control on
the reliability of his data, and there is nothing wrong in principle with wanting
to know who an ancient author's sources were.

An excessive (not to say obsessive)
form of Quellenforschung characterized ancient historiography in the
latter part of the 19th and earlier part of the 20th centuries and first grew
in the fertile soil of the great German universities. By the time its excesses
caused it to be downgraded as a method it had been practiced in all parts of
the world. It is now in severe disrepute despite some undeniable successes (if
you are interested in the "Q" source of the Gospels, you are touching
on one of the more successful results of Quellenforschung. That "Q"
is shorthand for Quelle, "source"--an example of an "author
X"). Among the problems with it are the following:

1) It can blind a researcher to idiosyncratic
modes of writing by the ancient author. If an ancient historian has an entertaining,
flowing style in general and you encounter a dense patch of hard analytic reasoning,
is that copied from a source with a different style, or has your author just
suddenly focussed more closely on his topic? Conflicting opinions or deviations
from uniformity may wrongly be attributed to the influence of a source author.

2) There was a "Gesetz
der Quellenbenützung" (law of source use) advanced by a scholar
named Heinrich Nissen in the mid-19th century. He posited that ancient authors
tended to use only one source at a time, and this rapidly crystallized into
the working assumption that ancient authors basically only could consult one
source at a time. The justification was that if you use a papyrus scroll,
it will fill up your desk (or workspace) as it unrolls, and that having more
than one scroll open at once would lead to difficulty. I've simplified a long
discussion almost to the point of caricature here, but even in its least extreme
form the idea of such a "law" of source use is problematic because the
assumption that an author used only one source at a time is dangerously convenient and so
seductive that it offers a specious justification which scholars were all too
quick to grab at. This line of thought takes no consideration of those plucky
individuals who somehow stumbled through using more than one scroll at a time;
authors who didn't think like we do in terms of verbatim quotes but relied on
their memory; the perhaps natural human tendency to mix what you already knew
in with what you are taking from a source; and the possibility of a mixture
of source materials not just from juggling scrolls, but from notes taken in
separate reading campaigns and then brought together in producing a final text.

3) I linked to this node from Appian
of Alexandria because he is the poster child of an ancient historian who was
vivisected by modern scholars seeking his vitals--his heart was a 'reliable'
discussion of the Roman civil wars supposedly taken from eyewitness Asinius
Pollio; his liver was special material on the triumviral period garnered from
Augustus' memoirs; no brain was found. None of these putative sources survives in any
form permitting us to see if Appian actually used them. Worst of all, Appian
himself was lost in the piecing out of his history, while the parts taken from
it were pieced back together into Frankenstein monster reconstructions of
Pollio's lost history, etc.

For a worthwhile account
of the dissapointments of Quellenforschung (in a discussion on Appian),
have a look at the first couple of pages of a good article in English by Brian
C. McGing, entitled "Appian's Mithridateios." It is in a
series called Aufstieg und Niedergang der römischen Welt (ANRW)--pages
496-522 of volume 34, part 1 of the portion of ANRW devoted to the
Roman Empire (II). (The volume cover will say II 34.1--gotta love those German
partitioning schemes.)

German readers can go right to the
source and read a particularly hair-raising account of a botched vivisection
in the regrettable Ernst Kornemann's 1921 article "Die unmittelbare Vorlage
von Appians Emphylia," in the journal Klio, volume 17
(1921) 33-43. You'll need access to a pretty good university research library
(or interlibrary loan) to get that one. If you can look into the face of the
gorgon and live, try Kornemann's 1898 "Die historische Schriftstellerei
des C. Asinius Pollio, zugleich ein Beitrag zur Quellenforschung über Appian
und Plutarch,"in Jahrbücher für classische Philologie
Supplementband 22 (1896) 557-691, which set historiographical study of
all three ancient authors mentioned in its title back by 50 years.